The modern biwas used in Japanese music can be classified into two groups, ‘‘Satsuma’’ biwa and ‘‘Chikuzen’’ biwa. In this paper, the structural difference between Chinese biwas (PiPa) and Satsuma biwas [especially the fret height and ‘‘torikuchi’’ (nut), related to ‘‘sawari’’], which have the same origin, are discussed by one of the authors, Y. Tohnai. Tohnai is a skilled player and a researcher of modern biwas. Three Satsuma biwas, with approximately the same size and shape but from different generations, were selected from Tohnai’s collection. The open strings of all three were played three times by Tohnai in an anechoic chamber; the tones were recorded on DAT and analyzed using a sound spectrograph and FFT analyzer. The most prominent result, common to all the tones, is that the sound-pressure level of the fundamental tone and lower overtones is very low compared with 6–12th overtones (from −40 to −30 dB). Psychological experiments must be carried out in order to study its influence on the sensation of ‘‘pitch.’’

This paper reports real-time subjective listening tests to examine the relationship between the adaptive filter tap length of acoustic echo canceller and the acoustic environmental conditions. A real-time acoustic echo canceller simulation system, for the listening tests, includes two digital filter boards which calculate acoustic echo, pseudo echo, and output error signal by subtracting the pseudo echo from the acoustic echo. Subjects judge whether they could recognize the error signal or not by using several acoustic echo cancellers with tap lengths differ from each other. Reverberation times in the room, signal delay time in telephone line, and noise level in the received signals are varied as parameters. As a result: The tap length mainly depends on reverberation time and delay time in the telecommunication system. The noise affects mildly. And, the maximum range of temporal masking by subject's voice is estimated as between 0.2 and 0.3 seconds.

Using the finite-element method (FEM), glassharp vibration was analyzed. Results show that the glassharp pitch is controllable at the stage of manufacturing. First, the effects of several factors were studied, such as geometry approximation, element type, and the number of division on the accuracy of mode frequencies. Second, it was examined how each mode frequency changes by the fixed position and length of the glassharp stem. The results demonstrate that their influences were of no great importance. Third, the pitch was widely adjustable by changing the swell of the cup. Particularly, it was finely adjustable by cutting a small circular groove inside a bottom of the cup instead of a conventional method.

Abstract:In this paper, we introduce a new percussion instrument, "hokyo," made of a particular stone, "Sanukite," and study its vibrational properties. The hokyo has a unique and somewhat complicated structure. Vibrational modes of the hokyo were analyzed by the finite element method, and their existence was verified by fast Fourier analysis of its tone and experimental modal analysis. The vibrational modes of the hokyo are principally determined by the rather simple behavior of the centered inner rod with a quasi-fixed end and a free end. The term "quasi-fixed end" means that the inner rod is not fixed exactly but only approximately at the base. The important modes of the inner rod are the fundamental bending mode, the torsional mode, and the longitudinal mode. The out of phase motion between the inner rod and the outer frame of a hokyo, coupled to each other by the base, produces a quasi-fixed boundary condition at the base. The quasi-fixed end gives a practical advantage to the hokyo in that it can shorten the length of the instrument very much compared to the instrument with free ends.

The phrase ‘‘con sordino’’ is used for the score of a violin family to indicate the use of a mute. The mute is used to reduce the volume of the violin tones and change their tone quality. This paper examines the influence of the weight of mutes on tones of a violin using the spectral envelopes of the violin tones. Violins with and without mutes were played by a skilled player in an anechoic chamber to produce tone samples which were then recorded on a DAT recorder. Using the tone samples, the time variances of the fundamentals and spectral envelopes obtained by FFT analyses were examined. The force transfer function of a cello bridge with mutes installed, which is used for convenience, was measured. From these examinations and analyses, we made the following observations: (1) the higher the order of harmonics, the lower their relative sound pressure levels compared with that of the fundamental and (2) the level differences between the peaks and dips of the spectral envelopes are reduced as the weight of a mute is increased.